Aligning agent for liquid-crystal cells

ABSTRACT

An alignment treating agent for a liquid crystal cell, which is composed mainly of a polyimide and/or a polyimide precursor made by a reaction for polymerization of a tetracarboxylic acid derivative component with a diamine component, wherein at least one part of the diamine component is a diamine component of the following formula (1): ##STR1## wherein n is an integer of from 1 to 12, and which gives a tilt angle of at most 2° to nematic liquid crystal.

This application is a 371 of PCT/SP97/02397, filed Jul. 10, 1997.

TECHNICAL FIELD

The present invention relates to an alignment treating agent for aliquid crystal cell. More particularly, it relates to an alignmenttreating agent for a liquid crystal cell wherein nematic liquid crystalmolecules have a low tilt angle to a substrate, an excellent alignmentstability can be obtained with no change in the tilt angle during heattreatment after injection of liquid crystal, and an excellent uniformityin alignment of ferroelectric liquid crystal or antiferroelectric liquidcrystal can be obtained.

BACKGROUND ART

A liquid crystal display device is a display device utilizingelectro-optic changes of liquid crystal. Attention has been drawn to itscharacteristic such as small lightweight of the device or smallconsumption of electric power, and it has been developed significantlyas a display device for various kinds of displays. Among these, a fieldeffect type liquid crystal display device of twisted nematic type (TNtype) is a typical example, wherein nematic liquid crystal havingpositive dielectric anisotropy is used, liquid crystal molecules arealigned in parallel to a substrate at the interface of each of a pair ofelectrode substrates facing each other, and the substrates are arrangedso that the alignment directions of liquid crystal molecules areperpendicular to each other.

With regard to such a liquid crystal display device of TN type, it isimportant to align liquid crystal molecules so that the major axisdirection of liquid crystal molecules is uniformly parallel to thesubstrate surface, and further liquid crystal molecules have a certaintilt angle to the substrate.

As typical methods to align liquid crystal molecules, two methods havebeen known. One method is to form an inorganic film on a substrate byvapor-depositing an inorganic substance such as silicon dioxideobliquely to the substrate, and to align liquid crystal molecule in thedirection of vapor deposition. By this method, a stable alignment havinga certain tilt angle can be obtained, but it is not industriallyeffective. The other method is to form an organic coating film on asubstrate surface, to rub the surface with a cloth such as cotton, nylonor polyester in a predetermined direction, and to align liquid crystalmolecules in the rubbing direction. By this method, stable alignment canbe obtained relatively easily, and thus this method is mainly employedindustrially. As the organic film, a polyvinyl alcohol, apolyoxyethylene, a polyamide or a polyimide may, for example, bementioned. However, in view of chemical stability and thermal stability,a polyimide is most commonly used. A typical example of the polyimideused for a liquid crystal alignment film is disclosed in JP-A-61-47932.

On the other hand, with regard to a ferroelectric liquid crystal displaydevice or an antiferroelectric liquid crystal display device, whereinferroelectric liquid crystal or antiferroelectric liquid crystal havingchiral smectic phase is used, and liquid crystal molecules are alignedat the interface of each of a pair of electrode substrates facing eachother so that the layer direction is oriented in one direction to thesubstrate, it has been known to have more excellent high speed responseand high angle of visibility as compared with a nematic liquid crystaldisplay device, due to direct interaction between the field and aspontaneous polarization of liquid crystal molecules. Further, withregard to a surface-stabilized ferroelectric liquid crystal device or asurface-stabilized antiferroelectric liquid crystal device wherein thecell gap is made thinner than a helical pitch of ferroelectric liquidcrystal or antiferroelectric liquid crystal, it has been known that adisplay device having bi-stability or tri-stability which can not beattained in a nematic liquid crystal display device and being highlyprecise even in a simple matrix electrode structure, can be prepared.

It is particularly important to align liquid crystal molecules uniformlyin a predetermined direction in the ferroelectric liquid crystal deviceor the antiferroelectric liquid crystal device. As a typical method toalign liquid crystal in such a manner, like in the case of the nematicliquid crystal display device, a method to form an inorganic film on asubstrate by vapor-depositing an inorganic substance such as silicondioxide obliquely, or a method to form an inductive coating film on asubstrate surface and to rub the surface with a cloth in a predetermineddirection, has been known. As the organic film to be rubbed, a polyimideis usually used, in view of chemical stability and thermal stability,like in the case of the nematic liquid crystal display device. However,with the conventional polyimide, the alignment of ferroelectric liquidcrystal or antiferroelectric liquid crystal was not necessarilysatisfactory. Further, even if an excellent alignment could be obtained,there were problems in the synthesis of the polyimide, such beingproblematic for the practical use.

With regard to the field effect type liquid crystal display device of TNtype wherein nematic liquid crystal having positive dielectricanisotropy is used, liquid crystal molecules are aligned in parallel toa substrate at the interface of each of a pair of electrode substratesfacing each other, and the substrates are arranged so that the alignmentdirections of liquid crystal molecules are perpendicular to each other,it is important to align liquid crystal molecules on the substratesurface, so that the major axis direction of liquid crystal molecules isuniformly parallel, and further, liquid crystal molecules have a certaintilt angle to the substrate. Particularly, in recent years, it isrequired to constantly obtain a low tilt angle of at most 2°, in orderto improve the contrast of the field effect type liquid crystal displaydevice of TN type.

However, with regard to a liquid crystal alignment film comprising aconventional polyimide, even if a low tilt angle was obtained afterinjection of liquid crystal, such a tilt angle sometimes changed when itwas heated at a temperature higher than the isotropic temperature ofliquid crystal (hereinafter referred to as isotropic treatment).Further, there was a problem that the tilt angle was likely to decreaseand alignment of liquid crystal molecules was in disorder by isotropictreatment. Such a problem must be solved in order to obtain more uniformliquid crystal display having higher contrast for liquid crystal displaydevices, and a polyimide alignment film which gives a low tilt angle ofat most 2° constantly against heat treatment, has been desired.

On the other hand, with regard to a ferroelectric liquid crystal deviceor an antiferroelectric liquid crystal device, it is very important toobtain an uniform initial alignment of liquid crystal, and it has beenknown that the alignment condition significantly affects performance ofa liquid crystal device. However, it is difficult to control thealignment condition of ferroelectric liquid crystal or antiferroelectricliquid crystal uniformly. Defects in alignment such as zigzag defectsare usually observed on the rubbed polyimide film, and they cause asignificant decrease in performance of the liquid crystal device such asa decrease in contrast, such being problematic. Further, as an alignmentfilm having ferroelectric liquid crystal aligned well, an aliphaticdiamine having an alkylene group in the main chain can be used, asdisclosed in JP-A-8-248424. However, such an aliphatic diamine is poorin reactivity for polymerization, and there were problems in respect toobtaining a predetermined polyimide varnish.

It is an object of the present invention to provide an alignmenttreating agent for a liquid crystal cell using nematic liquid crystal,wherein a liquid crystal alignment film having a low tilt angle beingstable against heat treatment, and an uniform liquid crystal displaywith high contrast can be obtained; and an alignment treating agent fora liquid crystal cell using ferroelectric liquid crystal orantiferroelectric liquid crystal, which controls the alignment conditionof liquid crystal uniformly.

DISCLOSURE OF THE INVENTION

The present invention relates to an alignment treating agent for aliquid crystal cell. The present inventors have intensively studied indetail and systematically the alignment treating agent for a liquidcrystal cell using nematic liquid crystal, which gives a low tilt anglebeing stable against heat treatment and as a result, have accomplishedthe present invention.

Namely, the present invention relates to an alignment treating agent fora liquid crystal cell, which is composed mainly of a polyimide and/or apolyimide precursor made by a reaction for polymerization of atetracarboxylic acid derivative component with a diamine component,wherein at least one part of the diamine component is adiamine of thefollowing formula (1): ##STR2## wherein n is an integer of from 1 to 12,and which gives a tilt angle of at most 2° to nematic liquid crystal.

BEST MODE FOR CARRYING OUT THE INVENTION

Now, the present invention will be described in further detail. Thediamine of the formula (1) to be used in the present invention issynthesized usually as follows. An α, ω-dihalogenoalkane and nitrophenolare dissolved in acetonitrile at a molar ratio of 1:2, and the reactionmixture is refluxed at a temperature of 80° C. in the coexistence ofpotassium carbonate, to obtain a dinitro compound. The dinitro compoundis reduced to obtain the diamine of the formula (1). As a method ofreduction, catalytic hydrogenation using palladium-carbon (Pd/C)catalyst under room temperature may, for example, be mentioned.

The treating agent for liquid crystal alignment of the present inventioncomprises a polyimide and/or a polyimide precursor having a certaindiamine structure. A resin solution having such a polyimide and/or apolyimide precursor dissolved in an organic polar solvent is coated on asubstrate provided with transparent electrodes, followed by drying andbaking to form a polyimide resin film, and the film surface is subjectedto alignment treatment such as rubbing treatment to use it as a liquidcrystal alignment film.

With regard to the treating agent for liquid crystal alignment of thepresent invention, nematic liquid crystal molecules have a low tiltangle to the substrate, and good alignment with no change in the tiltangle by heat treatment can be obtained. Further, when the treatingagent for liquid crystal alignment having such a performance is used asan alignment treating agent for ferroelectric liquid crystal orantiferroelectric liquid crystal, good alignment can be obtained.

The tetracarboxylic dianhydride and its derivative to be used in thepresent invention may, for example, be an aromatic tetracarboxylic acidsuch as pyromellitic acid, benzophenone tetracarboxylic acid, biphenyltetracarboxylic acid or naphthalene tetracarboxylic acid, itsdianhydride or its dicarboxylic acid diacid halide; an alicyclictetracarboxylic acid such as cyclobutane tetracarboxylic acid,cyclopentane tetracarboxylic acid, cyclohexane tetracarboxylic acid or3,4-dicarboxy-1,2,3,4-tetrahydro-1-naphthalene succinic acid, itsdianhydride or its dicarboxylic acid diacid halide; an aliphatictetracarboxylic acid such as butane tetracarboxylic acid, itsdianhydride or its dicarboxylic acid diacid halide. Among these, anaromatic tetracarboxylic acid such as pyromellitic acid or cyclobutanetetracarboxylic acid is particularly preferred, in order to obtain anadequate effect of the present invention.

Such tetracarboxylic acids or their derivatives may be used alone or incombination as a mixture of two or more of them.

As the diamine component of the formula (1) ##STR3## wherein n is aninteger of from 1 to 12, a bis(4-aminophenoxy)alkane of the formula (2)##STR4## wherein n is an integer of from 1 to 12, is practicallypreferred.

n in the formula (1) and the formula (2) is usually from 1 to 12,preferably from 1 to 10, more preferably from 1 to 8, since heatresistance of the obtained polyimide tends to decrease if n becomesbigger.

Specific examples of the formula (2) include bis(4-aminophenoxy)methane,1,2-bis(4-aminophenoxy)ethane, 1,3-bis(4-aminophenoxy)propane,1,4-bis(4-aminophenoxy)butane, 1,5-bis(4-aminophenoxy)pentane,1,6-bis(4-aminophenoxy)hexane, 1,7-bis(4-aminophenoxy)heptane,1,8-bis(4-aminophenoxy)octane, 1,9-bis(4-aminophenoxy)nonane and1,10-bis(4-aminophenoxy)decane.

Particularly, 1,3-bis(4-aminophenoxy)propane,1,4-bis(4-aminophenoxy)butane, 1,5-bis(4-aminophenoxy)pentane,1,6-bis(4-aminophenoxy)hexane, 1,7-bis(4-aminophenoxy)heptane, and1,8-bis(4-aminophenoxy)octane are preferred.

The amount of the diamine component of the formula (1) to the totaldiamine component is not particularly limited, so long as a low tiltangle of at most 2° of nematic liquid crystal can be obtained. However,it is usually from 50 to 100 mol %, preferably from 70 to 100 mol %,particularly preferably from 85 to 100 mol %.

As examples of diamines other than the diamine component of the formula(1) of the present invention, specific examples may be mentioned whichinclude aromatic diamines such as 2,5-diaminotoluene,2,6-diaminotoluene, 4,4'-diaminobiphenyl,3,3'-dimethyl-4,4'-diaminobiphenyl, 3,3'-dimethoxy-4,4'-diaminobiphenyl,diaminodiphenyl ether, 2,2'-diaminodiphenylpropane,bis(3,5-diethyl4-aminophenyl)methane, diaminodiphenylsulfone,diaminobenzophenone, diaminonaphthalene, 1,4-bis(4-aminophenoxy)benzene,1,4-bis(4-aminophenyl)benzene, 9,10-bis(4-aminophenyl)anthracene,1,3-bis(4-aminophenoxy)benzene, 4,4'-bis(4-aminophenoxy)diphenylsulfoneand 2,2-bis[4-(4-aminophenoxy)phenyl]propane, alicyclic diamines such asbis(4-aminocyclohexyl)methane andbis(4-amino-3-methylcyclohexyl)methane, and diaminocyclohexanes such as##STR5## wherein m is an integer of from 1 to 10.

These diamines may be used alone or in combination as a mixture of twoor more of them.

A tetracarboxylic dianhydride and a diamine are reacted and polymerizedto obtain a polyimide precursor. As the tetracarboxylic acid derivativeto be used, a tetracarboxylic dianhydride is usually used. The molarratio of the tetracarboxylic dianhydride to the diamine is preferablyfrom 0.8 to 1.2. Like in the normal condensation polymerization, thecloser to 1 the molar ratio, the higher the polymerization degree of thepolymer produced.

If the polymerization degree is too small, the strength of the polyimidecoating film is inadequate, and if the polymerization degree is toohigh, work efficiency during forming of the polyimide coating film islikely to deteriorate. Accordingly, the polymerization degree of thereaction product of the present invention calculated as a reducedviscosity of a polyimide precursor solution, is preferably from 0.05 to5.0 dl/g (as measured in N-methylpyrrolidone at a temperature of 30° C.and at a concentration of 0.5 g/dl.

As a method of reacting and polymerizing a tetracarboxylic dianhydridewith a primary diamine, a solution polymerization method is usuallypreferred. Specific examples of a solvent to be used for the solutionpolymerization method include N,N-dimethylformamide,N,N-dimethylacetamide, N-methyl-2-pyrrolidone, N-methylcaprolactam,dimethylsulfoxide, tetramethylurea, pyridine, dimethylsulfone,hexamethylphosphoramide and butyllactone. These may be used alone or incombination as a mixture. Further, a solvent which does not dissolve thepolyimide resin precursor, may be added to the above solvent in anamount within such a range that an uniform solution can still beobtained. The reaction temperature can be selected optionally within arange of from -20° C. to 150° C., preferably from -5° C. to 100° C.

To convert the polyimide resin precursor to the polyimide resin, amethod of heating for dehydration ring-closure is employed. The heatingtemperature for dehydration ring-closure can be selected optionallywithin a range of from 150° C. to 450° C., preferably from 170° C. to350° C. The time required for the dehydration ring-closure is usuallyfrom 30 seconds to 10 hours, preferably from 5 minutes to 5 hours,although it varies depending upon the reaction temperature.

Further, in the case where the polyimide is a so-called solublepolyimide which is soluble in an organic solvent, a polyimide precursorobtained by reacting a tetracarboxylic dianhydride and a primary diaminecan be imide-modified by using a known dehydration ring-closure catalystin a solution.

The polyimide resin solution thus obtained may be used as it is, or maybe used as dissolved again in a poor solvent such as methanol orethanol.

The solvent is not particularly limited so long as it dissolves theobtained polyimide resin again. It may, for example, be 2-pyrrolidone,N-methylpyrrolidone, N-ethylpyrrolidone, N-vinylpyrrolidone,N,N-dimethylacetamide, N,N-dimethylformamide, γ-butyllactone or diglyme.

The polyimide and/or the polyimide precursor solution of the presentinvention obtained as mentioned above, is coated on a transparentsubstrate of e.g. glass or plastic provided with transparent electrodesby a method such as a spin coating or transfer printing method, followedby heat treatment under the above conditions to form a polyimide film.The thickness of the polyimide film is not particularly limited, but itis preferably from 100 Å to 3000 Å, to be used for a liquid crystalalignment film. Then, the resin film is subjected to an alignmenttreatment such as rubbing treatment to obtain a treating agent forliquid crystal alignment.

Now, the present invention will be described in further detail withreference to Examples. However, it should be understood that the presentinvention is by no means restricted to such specific Examples.

EXAMPLE 1

22.8 g (0.1 mol) of 1,4-bis(4-aminophenoxy)butane and 19.2 g (0.098 mol)of 1,2,3,4-cyclobutane tetracarboxylic dianhydride were reacted in 343.5g of N-methylpyrrolidone (hereinafter referred to as NMP for short) for10 hours at room temperature to prepare a polyimide precursor (polyamicacid) solution. The polymerization reaction proceeded easily anduniformly, and a polyimide precursor having a reduced viscosity of 0.9dl/g (as measured in NMP at a temperature of 30° C. and at aconcentration of 0.5 g/dl), was obtained.

This solution was diluted with NMP to a total solid content of 4 wt %.Then, the solution was spin-coated at 3500 rpm on glass substrates andthen subjected to heat treatment at 80° C. for 5 minutes and at 250° C.for one hour to form polyimide resin films having a thickness of 1000 Å.

The coating films were rubbed with a cloth and assembled with a spacerof 50 μm interposed therebetween so that the respective rubbingdirections are opposingly in parallel with each other, and nematicliquid crystal (ZLI-2293, manufactured by Merck Co.) was injected intothe space to obtain a liquid crystal cell.

The alignment condition of the liquid crystal cell was observed by apolarization microscope, and confirmed to be uniform with no defect.Further, with respect to the cell, the tilt angle of liquid crystal wasmeasured by a crystal rotation method and found to be 1.0°. Thus, thetilt angle was low and stable.

Further, the liquid crystal cell was subjected to heat treatment in anoven at a temperature of 120° C. for one hour, and the alignmentcondition was observed by a polarization microscope, whereby an uniformalignment with no defect was confirmed. Further, with regard to thecell, the tilt angle of liquid crystal was measured by a crystalrotation method and found to be 1.0°. Thus, the tilt angle was low.

EXAMPLE 2

24.2 g (0.1 mol) of 1,5-bis(4-aminophenoxy)pentane and 19.2 g (0.098mol) of 1,2,3,4-cyclobutane tetracarboxylic dianhydride were reacted in343.5 g of N-methylpyrrolidone (hereinafter referred to as NMP forshort) for 10 hours at room temperature to prepare a polyimide precursor(polyamic acid) solution. The polymerization reaction proceeded easilyand uniformly, and a polyimide precursor having a reduced viscosity of0.8 dl/g (as measured in NMP at a temperature of 30° C. and at aconcentration of 0.5 g/dl), was obtained.

This solution was diluted with NMP to a total solid content of 4 wt %.Then, the solution was spin-coated at 3500 rpm on glass substrates andthen subjected to heat treatment at 80° C. for 5 minutes and at 250° C.for one hour to form polyimide resin films having a thickness of 1000 Å.

The coating films were rubbed with a cloth and assembled with a spacerof 50 μm interposed therebetween so that the respective rubbingdirections are opposingly in parallel with each other, and nematicliquid crystal (ZLI-2293, manufactured by Merck Co.) was injected intothe space to obtain a liquid crystal cell.

The alignment condition of the liquid crystal cell was observed by apolarization microscope, and confirmed to be uniform with no defect.Further, with respect to the cell, the tilt angle of liquid crystal wasmeasured by a crystal rotation method and found to be 0.9°. Thus, thetilt angle was low.

Further, the liquid crystal cell was subjected to heat treatment in anoven at a temperature of 1200 for one hour, and the alignment conditionwas observed by a polarization microscope, whereby an uniform alignmentwith no defect was confirmed. Further, with regard to the cell, the tiltangle of liquid crystal was measured by a crystal rotation method andfound to be 1.0°. Thus, the tilt angle was low and stable.

EXAMPLE 3

34.2 g (0.1 mol) of 1,9-bis(4-aminophenoxy)nonane and 19.2 g (0.098 mol)of 1,2,3,4-cyclobutane tetracarboxylic dianhydride were reacted in 302.6g of N-methylpyrrolidone (hereinafter referred to as NMP for short) for10 hours at room temperature to prepare a polyimide precursor (polyamicacid) solution. The polymerization reaction proceeded easily anduniformly, and a polyimide precursor having a reduced viscosity of 0.75dl/g (as measured in NMP at a temperature of 30° C. and at aconcentration of 0.5 g/dl), was obtained.

This solution was diluted with NMP to a total solid content of 4 wt %.Then, the solution was spin-coated at 3000 rpm on glass substrates andthen subjected to heat treatment at 80° C. for 5 minutes and at 250° C.for one hour to form polyimide resin films having a thickness of 1000 Å.

The coating films were rubbed with a cloth and assembled with a spacerof 50 μm interposed therebetween so that the respective rubbingdirections are opposingly in parallel with each other, and nematicliquid crystal (ZLI-2293, manufactured by Merck Co.) was injected intothe space to obtain a liquid crystal cell.

The alignment condition of the liquid crystal cell was observed by apolarization microscope, and confirmed to be uniform with no defect.Further, with respect to the cell, the tilt angle of liquid crystal wasmeasured by a crystal rotation method and found to be 0.9°. Thus, thetilt angle was low.

Further, the liquid crystal cell was subjected to heat treatment in anoven at a temperature of 120° C. for one hour, and the alignmentcondition was observed by a polarization microscope, whereby an uniformalignment with no defect was confirmed. Further, with regard to thecell, the tilt angle of liquid crystal was measured by a crystalrotation method and found to be 0.9°. Thus, the tilt angle was low andstable.

EXAMPLE 4

38.4 g (0.1 mol) of 1,12-bis(4-aminophenoxy)dodecane and 19.2 g (0.098mol) of 1,2,3,4-cyclobutane tetracarboxylic dianhydride were reacted in326.4 g of N-methylpyrrolidone (hereinafter referred to as NMP forshort) for 10 hours at room temperature to prepare a polyimide precursor(polyamic acid) solution. The polymerization reaction proceeded easilyand uniformly, and a polyimide precursor having a reduced viscosity of0.70 dl/g (as measured in NMP at a temperature of 30° C. and at aconcentration of 0.5 g/dl), was obtained.

This solution was diluted with NmP to a total solid content of 4 wt %.Then, the solution was spin-coated at 2800 rpm on glass substrates andthen subjected to heat treatment at 80° C. for 5 minutes and at 250° C.for one hour to form polyimide resin films having a thickness of 1000 Å.

The coating films were rubbed with a cloth and assembled with a spacerof 50 μm interposed therebetween so that the respective rubbingdirections are opposingly in parallel with each other, and nematicliquid crystal (ZLI-2293, manufactured by Merck Co.) was injected intothe space to obtain a liquid crystal cell.

The alignment condition of the liquid crystal cell was observed by apolarization microscope, and confirmed to be uniform with no defect.Further, with respect to the cell, the tilt angle of liquid crystal wasmeasured by a crystal rotation method and found to be 1.7°. Thus, thetilt angle was low.

Further, the liquid crystal cell was subjected to heat treatment in anoven at a temperature of 120° C. for one hour, and the alignmentcondition was observed by a polarization microscope, whereby an uniformalignment with no defect was confirmed. Further, with regard to thecell, the tilt angle of liquid crystal was measured by a crystalrotation method and found to be 1.7°. Thus, the tilt angle was low andstable.

EXAMPLE 5

12.1 g (0.05 mol) of 1,5-bis(4-aminophenoxy)pentane, 10.1 g (0.05 mol)of diaminodiphenyl ether and 19.2 g (0.098 mol) of 1,2,3,4-cyclobutanetetracarboxylic dianhydride were reacted in 234.6 g ofN-methylpyrrolidone (hereinafter referred to as NMP for short) for 10hours at room temperature to prepare a polyimide precursor (polyamicacid) solution. The polymerization reaction proceeded easily anduniformly, and a polyimide precursor having a reduced viscosity of 0.86dl/g (as measured in NMP at a temperature of 30° C. and at aconcentration of 0.5 g/dl), was obtained.

This solution was diluted with NMP to a total solid content of 4 wt %.Then, the solution was spin-coated at 3500 rpm on glass substrates andthen subjected to heat treatment at 80° C. for 5 minutes and at 250° C.for one hour to form polyimide resin films having a thickness of 1000 Å.

The coating films were rubbed with a cloth and assembled with a spacerof 50 μm interposed therebetween so that the respective rubbingdirections are opposingly in parallel with each other, and nematicliquid crystal (ZLI-2293, manufactured by Merck Co.) was injected intothe space to obtain a liquid crystal cell.

The alignment condition of the liquid crystal cell was observed by apolarization microscope, and confirmed to be uniform with no defect.Further, with respect to the cell, the tilt angle of liquid crystal wasmeasured by a crystal rotation method and found to be 1.9°. Thus, thetilt angle was low.

Further, the liquid crystal cell was subjected to heat treatment in anoven at a temperature of 120° C. for one hour, and the alignmentcondition was observed by a polarization microscope, whereby an uniformalignment with no defect was confirmed. Further, with regard to thecell, the tilt angle of liquid crystal was measured by a crystalrotation method and found to be 1.9°. Thus, the tilt angle was low andstable.

EXAMPLE 6

19.4 g (0.08 mol) of 1,5-bis(4-aminophenoxy)pentane, 4 g (0.02 mol) ofdiaminodiphenyl ether and 19.2 g (0.098 mol) of 1,2,3,4-cyclobutanetetracarboxylic dianhydride were reacted in 241.4 g ofN-methylpyrrolidone (hereinafter referred to as NMP for short) for 10hours at room temperature to prepare a polyimide precursor (polyamicacid) solution. The polymerization reaction proceeded easily anduniformly, and a polyimide precursor having a reduced viscosity of 0.86dl/g (as measured in NMP at a temperature of 30° C. and at aconcentration of 0.5 g/dl), was obtained.

This solution was diluted with NMP to a total solid content of 4 wt %.Then, the solution was spin-coated at 4000 rpm on glass substrates andthen subjected to heat treatment at 80° C. for 5 minutes and at 250° C.for one hour to form polyimide resin films having a thickness of 1000 Å.

The coating films were rubbed with a cloth and assembled with a spacerof 50 μm interposed therebetween so that the respective rubbingdirections are opposingly in parallel with each other, and nematicliquid crystal (ZLI-2293, manufactured by Merck Co.) was injected intothe space to obtain a liquid crystal cell.

The alignment condition of the liquid crystal cell was observed by apolarization microscope, and confirmed to be uniform with no defect.Further, with respect to the cell, the tilt angle of liquid crystal wasmeasured by a crystal rotation method and found to be 1.7°. Thus, thetilt angle was low.

Further, the liquid crystal cell was subjected to heat treatment in anoven at a temperature of 120° C. for one hour, and the alignmentcondition was observed by a polarization microscope, whereby an uniformalignment with no defect was confirmed. Further, with regard to thecell, the tilt angle of liquid crystal was measured by a crystalrotation method and found to be 1.7°. Thus, the tilt angle was low andstable.

EXAMPLE 7

22.8 g (0.1 mol) of 1,4-bis(4-aminophenoxy)butane and 21.8 g (0.096 mol)of pyromellitic dianhydride were reacted in 252.7 g ofN-methylpyrrolidone (hereinafter referred to as NMP for short) for 10hours at room temperature to prepare a polyimide precursor (polyamicacid) solution. The polymerization reaction proceeded easily anduniformly, and a polyimide precursor having a reduced viscosity of 0.92dl/g (as measured in NMP at a temperature of 30° C. and at aconcentration of 0.5 g/dl), was obtained.

This solution was diluted with NMP to a total solid content of 4 wt %.Then, the solution was spin-coated at 4000 rpm on glass substrates andthen subjected to heat treatment at 80° C. for 5 minutes and at 250° C.for one hour to form polyimide resin films having a thickness of 1000 Å.

The coating films were rubbed with a cloth and assembled with a spacerof 50 μm interposed therebetween so that the respective rubbingdirections are opposingly in parallel with each other, and nematicliquid crystal (ZLI-2293, manufactured by Merck Co.) was injected intothe space to obtain a liquid crystal cell.

The alignment condition of the liquid crystal cell was observed by apolarization microscope, and confirmed to be uniform with no defect.Further, with respect to the cell, the tilt angle of liquid crystal wasmeasured by a crystal rotation method and found to be 0.9°. Thus, thetilt angle was low.

Further, the liquid crystal cell was subjected to heat treatment in anoven at a temperature of 120° C. for one hour, and the alignmentcondition was observed by a polarization microscope, whereby an uniformalignment with no defect was confirmed. Further, with regard to thecell, the tilt angle of liquid crystal was measured by a crystalrotation method and found to be 0.9°. Thus, the tilt angle was low andstable.

EXAMPLE 8

31.4 g (0.1 mol) of 1,7-bis(4-aminophenoxy)heptane and 19.2 g (0.098mol) of 1,2,3,4-cyclobutane tetracarboxylic dianhydride were reacted in286.7 g of N-methylpyrrolidone (hereinafter referred to as NMP forshort) for 10 hours at room temperature to prepare a polyimide precursor(polyamic acid) solution. The polymerization reaction proceeded easilyand uniformly, and a polyimide precursor having a reduced viscosity of0.76 dl/g (as measured in NMP at a temperature of 30° C. and at aconcentration of 0.5 g/dl), was obtained with good reproducibility.

This solution was diluted with NMP to a total solid content of 4 wt %.Then, the solution was spin-coated at 3000 rpm on glass substrates andthen subjected to heat treatment at 80° C. for 5 minutes and at 250° C.for one hour to form polyimide resin films having a thickness of 1000 Å.

The coating films were rubbed with a cloth and assembled with a spacerof 50 μm interposed therebetween so that the respective rubbingdirections are opposingly in parallel with each other, and nematicliquid crystal (ZLI-2293, manufactured by Merck Co.) was injected intothe space to obtain a liquid crystal cell.

The alignment condition of the liquid crystal cell was observed by apolarization microscope, and confirmed to be uniform with no defect.Further, with respect to the cell, the tilt angle of liquid crystal wasmeasured by a crystal rotation method and found to be 1.0°. Thus, thetilt angle was low.

Further, the liquid crystal cell was subjected to heat treatment in anoven at a temperature of 120° C. for one hour, and the alignmentcondition was observed by a polarization microscope, whereby an uniformalignment with no defect was confirmed. Further, with regard to thecell, the tilt angle of liquid crystal was measured by a crystalrotation method and found to be 1.0°. Thus, the tilt angle was low andstable.

EXAMPLE 9

24.2 g (0.1 mol) of 1,5-bis(4-aminophenoxy)pentane and 21.8 g (0.096mol) of pyromellitic dianhydride were reacted in 260.6 g ofN-methylpyrrolidone (hereinafter referred to as NMP for short) for 10hours at room temperature to prepare a polyimide precursor (polyamicacid) solution. The polymerization reaction proceeded easily anduniformly, and a polyimide precursor having a reduced viscosity of 0.94dl/g (as measured in NMP at a temperature of 30° C. and at aconcentration of 0.5 g/dl), was obtained with good reproducibility.

This solution was diluted with NMP to a total solid content of 4 wt %.Then, the solution was spin-coated at 4500 rpm on glass substrates andthen subjected to heat treatment at 80° C. for 5 minutes and at 250° C.for one hour to form polyimide resin films having a thickness of 1000 Å.

The coating films were rubbed with a cloth and assembled with a spacerof 50 μm interposed therebetween so that the respective rubbingdirections are opposingly in parallel with each other, and nematicliquid crystal (ZLI-2293, manufactured by Merck Co.) was injected intothe space to obtain a liquid crystal cell.

The alignment condition of the liquid crystal cell was observed by apolarization microscope, and confirmed to be uniform with no defect.Further, with respect to the cell, the tilt angle of liquid crystal wasmeasured by a crystal rotation method and found to be 0.9°. Thus, thetilt angle was low.

Further, the liquid crystal cell was subjected to heat treatment in anoven at a temperature of 120° C. for one hour, and the alignmentcondition was observed by a polarization microscope, whereby an uniformalignment with no defect was confirmed. Further, with regard to thecell, the tilt angle of liquid crystal was measured by a crystalrotation method and found to be 0.9°. Thus, the tilt angle was low andstable.

EXAMPLE 10

The same polyimide precursor (polyamic acid) solution as used in Example1 was prepared. Namely, 22.8 g (0.1 mol) of1,4-bis(4-aminophenoxy)butane and 19.2 g (0.098 mol) of1,2,3,4-cyclobutane tetracarboxylic dianhydride were reacted in 343.5 gof N-methylpyrrolidone (hereinafter referred to as NMP for short) for 10hours at room temperature to prepare a polyimide precursor (polyamicacid) solution. The polymerization reaction proceeded easily anduniformly, and a polyimide precursor having a reduced viscosity of 0.9dl/g (as measured in NMP at a temperature of 30° C. and at aconcentration of 0.5 g/dl), was obtained.

This solution was diluted with NMP to a total solid content of 4 wt %,in the same manner as in Example 1. Then, the solution was spin-coatedat 3500 rpm on glass substrates and then subjected to heat treatment at80° C. for 5 minutes and at 250° C. for one hour to form polyimide resinfilms having a thickness of 1000 Å.

The coating films were rubbed with a cloth, and the substrates subjectedto such a rubbing treatment, were assembled with a spacer of 2 μminterposed therebetween so that the respective rubbing directions are inparallel with each other, and ferroelectric smectic liquid crystal(CS-1014, manufactured by Chisso Co.) was injected into the space toobtain a surface-stabilized liquid crystal cell. The alignment conditionof the cell was observed by a polarization microscope, and no defect wasfound at any region of the liquid crystal cell. Thus, an uniformalignment of ferroelectric liquid crystal was confirmed.

EXAMPLE 11

The same polyimide precursor (polyamic acid) solution as used in Example2 was prepared. Namely, 24.2 g (0.1 mol) of1,5-bis(4-aminophenoxy)pentane and 19.2 g (0.098 mol) of1,2,3,4-cyclobutane tetracarboxylic dianhydride were reacted in 343.5 gof N-methylpyrrolidone (hereinafter referred to as NMP for short) for 10hours at room temperature to prepare a polyimide precursor (polyamicacid) solution. The polymerization reaction proceeded easily anduniformly, and a polyimide precursor having a reduced viscosity of 0.8dl/g (as measured in NMP at a temperature of 30° C. and at aconcentration of 0.5 g/dl), was obtained.

This solution was diluted with NMP to a total solid content of 4 wt %,in the same manner as in Example 2. Then, the solution was spin-coatedat 3500 rpm on glass substrates and then subjected to heat treatment at80° C. for 5 minutes and at 250° C. for one hour to form polyimide resinfilms having a thickness of 1000 Å.

The coating films were rubbed with a cloth, and the substrates subjectedto such a rubbing treatment, were assembled with a spacer of 2 μminterposed therebetween so that the respective rubbing directions are inparallel with each other, and ferroelectric smectic liquid crystal(CS-1014, manufactured by Chisso Co.) was injected into the space toobtain a surface-stabilized liquid crystal cell. The alignment conditionof the cell was observed by a polarization microscope, and no defect wasfound at any region of the liquid crystal cell. Thus, an uniformalignment of ferroelectric liquid crystal was confirmed.

EXAMPLE 12

The same polyimide precursor (polyamic acid) solution as used in Example3 was prepared. Namely, 34.2 g (0.1 mol) of1,9-bis(4-aminophenoxy)nonane and 19.2 g (0.098 mol) of1,2,3,4-cyclobutane tetracarboxylic dianhydride were reacted in 302.6 gof N-methylpyrrolidone (hereinafter referred to as NMP for short) for 10hours at room temperature to prepare a polyimide precursor (polyamicacid) solution. The polymerization reaction proceeded easily anduniformly, and a polyimide precursor having a reduced viscosity of 0.75dl/g (as measured in NMP at a temperature of 30° C. and at aconcentration of 0.5 g/dl), was obtained.

This solution was diluted with NMP to a total solid content of 4 wt %,in the same manner as in Example 3. Then, the solution was spin-coatedat 3000 rpm on glass substrates and then subjected to heat treatment at80° C. for 5 minutes and at 250° C. for one hour to form polyimide resinfilms having a thickness of 1000 Å.

The coating films were rubbed with a cloth, and the substrates subjectedto such a rubbing treatment, were assembled with a spacer of 2 μminterposed therebetween so that the respective rubbing directions are inparallel with each other, and ferroelectric smectic liquid crystal(CS-1014, manufactured by Chisso Co.) was injected into the space toobtain a surface-stabilized liquid crystal cell. The alignment conditionof the cell was observed by a polarization microscope, and no defect wasfound at any region of the liquid crystal cell. Thus, an uniformalignment of ferroelectric liquid crystal was confirmed.

EXAMPLE 13

The same polyimide precursor (polyamic acid) solution as used in Example7 was prepared. Namely, 22.8 g (0.1 mol) of1,4-bis(4-aminophenoxy)butane and 21.8 g (0.096 mol) of pyromelliticdianhydride were reacted in 252.7 g of N-methylpyrrolidone (hereinafterreferred to as NMP for short) for 10 hours at room temperature toprepare a polyimide precursor (polyamic acid) solution. Thepolymerization reaction proceeded easily and uniformly, and a polyimideprecursor having a reduced viscosity of 0.92 dl/g (as measured in NMP ata temperature of 30° C. and at a concentration of 0.5 g/dl), wasobtained.

This solution was diluted with NMP to a total solid content of 4 wt %,in the same manner as in Example 7. Then, the solution was spin-coatedat 4000 rpm on glass substrates and then subjected to heat treatment at80° C. for 5 minutes and at 250° C. for one hour to form polyimide resinfilms having a thickness of 1000 Å.

The coating films were rubbed with a cloth, and the substrates subjectedto such a rubbing treatment, were assembled with a spacer of 2 μminterposed therebetween so that the respective rubbing directions are inparallel with each other, and ferroelectric smectic liquid crystal(CS-1014, manufactured by Chisso Co.) was injected into the space toobtain a surface-stabilized liquid crystal cell. The alignment conditionof the cell was observed by a polarization microscope, and no defect wasfound at any region of the liquid crystal cell. Thus, an uniformalignment of ferroelectric liquid crystal was confirmed.

EXAMPLE 14

The same polyimide precursor (polyamic acid) solution as used in Example8 was prepared. Namely, 31.4 g (0.1 mol) of1,7-bis(4-aminophenoxy)heptane and 19.2 g (0.098 mol) of1,2,3,4-cyclobutane tetracarboxylic dianhydride were reacted in 286.7 gof N-methylpyrrolidone (hereinafter referred to as NMP for short) for 10hours at room temperature to prepare a polyimide precursor (polyamicacid) solution. The polymerization reaction proceeded easily anduniformly, and a polyimide precursor having a reduced viscosity of 0.76dl/g (as measured in NMP at a temperature of 30° C. and at aconcentration of 0.5 g/dl), was obtained with good reproducibility.

This solution was diluted with NMP to a total solid content of 4 wt %,in the same manner as in Example 8. Then, the solution was spin-coatedat 3000 rpm on glass substrates and then subjected to heat treatment at80° C. for 5 minutes and at 250° C. for one hour to form polyimide resinfilms having a thickness of 1000 Å.

The coating films were rubbed with a cloth, and the substrates subjectedto such a rubbing treatment, were assembled with a spacer of 2 μminterposed therebetween so that the respective rubbing directions are inparallel with each other, and ferroelectric smectic liquid crystal(CS-1014, manufactured by Chisso Co.) was injected into the space toobtain a surface-stabilized liquid crystal cell. The alignment conditionof the cell was observed by a polarization microscope, and no defect wasfound at any region of the liquid crystal cell. Thus, an uniformalignment of ferroelectric liquid crystal was confirmed.

EXAMPLE 15

The same polyimide precursor (polyamic acid) solution as used in Example9 was prepared. Namely, 24.2 g (0.1 mol) of1,5-bis(4-aminophenoxy)pentane and 21.8 g (0.096 mol) of pyromelliticdianhydride were reacted in 260.6 g of N-methylpyrrolidone (hereinafterreferred to as NMP for short) for 10 hours at room temperature toprepare a polyimide precursor (polyamic acid) solution. Thepolymerization reaction proceeded easily and uniformly, and a polyimideprecursor having a reduced viscosity of 0.94 dl/g (as measured in NMP ata temperature of 30° C. and at a concentration of 0.5 g/dl), wasobtained with good reproducibility.

This solution was diluted with NMP to a total solid content of 4 wt %,in the same manner as in Example 9. Then, the solution was spin-coatedat 4500 rpm on glass substrates and then subjected to heat treatment at80° C. for 5 minutes and at 250° C. for one hour to form polyimide resinfilms having a thickness of 1000 Å.

The coating films were rubbed with a cloth, and the substrates subjectedto such a rubbing treatment, were assembled with a spacer of 2 μminterposed therebetween so that the respective rubbing directions are inparallel with each other, and ferroelectric smectic liquid crystal(CS-1014, manufactured by Chisso Co.) was injected into the space toobtain a surface-stabilized liquid crystal cell. The alignment conditionof the cell was observed by a polarization microscope, and no defect wasfound at any region of the liquid crystal cell. Thus, an uniformalignment of ferroelectric liquid crystal was confirmed.

COMPARATIVE EXAMPLE 1

20.0 g (0.1 mol) of diaminodiphenyl ether and 19.2 g (0.098 mol) of1,2,3,4-cyclobutane tetracarboxylic dianhydride were reacted in 343.5 gof N-methylpyrrolidone (hereinafter referred to as NMP for short) for 10hours at room temperature to prepare a polyimide precursor (polyamicacid) solution. The polymerization reaction proceeded easily anduniformly, and a polyimide precursor having a reduced viscosity of 0.98dl/g (as measured in NMP at a temperature of 30° C. and at aconcentration of 0.5 g/dl), was obtained.

This solution was diluted with NMP to a total solid content of 3 wt %.Then, the solution was spin-coated at 3000 rpm on glass substrates andthen subjected to heat treatment at 80° C. for 5 minutes and at 250° C.for one hour to form polyimide resin films having a thickness of 1000 Å.The coating films were rubbed with a cloth and assembled with a spacerof 50 μm interposed therebetween so that the respective rubbingdirections are opposingly in parallel with each other, and nematicliquid crystal (ZLI-2293, manufactured by Merck Co.) was injected intothe space to obtain a liquid crystal cell.

The alignment condition of the liquid crystal cell was observed by apolarization microscope, and confirmed to be uniform with no defect.Further, with respect to the cell, the tilt angle of liquid crystal wasmeasured by a crystal rotation method and found to be 3.6°.

Further, the liquid crystal cell was subjected to heat treatment in anoven at a temperature of 120° C. for one hour, and the alignmentcondition was observed by a polarization microscope, whereby an uniformalignment with no defect was found out. However, with regard to thecell, the tilt angle of liquid crystal was measured by a crystalrotation method and found to be 4.1°. Thus, the tilt angle became highby the heat treatment, and a low tilt angle could not be obtained afterheat treatment.

COMPARATIVE EXAMPLE 2

22.6 g (0.1 mol) of 4,4'-diamino-3,3'-dimethyldicyclohexylmethane and19.2 g (0.098 mol) of 1,2,3,4-cyclobutane tetracarboxylic dianhydridewere reacted in 343.5 g of N-methylpyrrolidone (hereinafter referred toas NMP for short) for 10 hours at room temperature to prepare apolyimide precursor (polyamic acid) solution. The polymerizationreaction proceeded easily and uniformly, and a polyimide precursorhaving a reduced viscosity of 0.78 dl/g (as measured in NMP at atemperature of 30° C. and at a concentration of 0.5 g/dl), was obtained.

This solution was diluted with NMP to a total solid content of 4 wt %.Then, the solution was spin-coated at 3500 rpm on glass substrates andthen subjected to heat treatment at 80° C. for 5 minutes and at 250° C.for one hour to form polyimide resin films having a thickness of 1000 Å.

The coating films were rubbed with a cloth and assembled with a spacerof 50 μm interposed therebetween so that the respective rubbingdirections are opposingly in parallel with each other, and nematicliquid crystal (ZLI-2293, manufactured by Merck Co.) was injected intothe space to obtain a liquid crystal cell.

The alignment condition of the liquid crystal cell was observed by apolarization microscope, and confirmed to be uniform with no defect.Further, with regard to the cell, the tilt angle of liquid crystal wasmeasured by a crystal rotation method and found to be 3.8°.

Further, the liquid crystal cell was subjected to heat treatment in anoven at a temperature of 120° C. for one hour, and the alignmentcondition was observed by a polarization microscope, whereby analignment condition with many defects was found out.

COMPARATIVE EXAMPLE 3

20.0 g (0.1 mol) of diaminodiphenyl ether and 19.2 g (0.098 mol) of1,2,3,4-cyclobutane tetracarboxylic dianhydride were reacted in 343.5 gof N-methylpyrrolidone (hereinafter referred to as NMP for short) for 10hours at room temperature to prepare a polyimide precursor (polyamicacid) solution. The polymerization reaction proceeded easily anduniformly, and a polyimide precursor having a reduced viscosity of 0.98dl/g (as measured in NMP at a temperature of 30° C. and at aconcentration of 0.5 g/dl), was obtained.

This solution was diluted with NMP to a total solid content of 3 wt %.Then, the solution was spin-coated at 3000 rpm on glass substrates andthen subjected to heat treatment at 80° C. for 5 minutes and at 250° C.for one hour to form polyimide resin films having a thickness of 1000 Å.The coating films were rubbed with a cloth, and the substrates subjectedto such rubbing treatment were assembled with a spacer of 2 μminterposed therebetween so that the respective rubbing directions are inparallel with each other, and ferroelectric smectic liquid crystal(CS-1014, manufactured by Chisso Co.) was injected into the space toobtain a surface-stabilized liquid crystal cell. The alignment conditionof the cell was observed by a polarization microscope, whereby manyzigzag defects and linear defects were found, and t he alignment offerroelectric liquid crystal was uniform.

COMPARATIVE EXAMPLE 4

22.6 g (0.1 mol) of 4,4'-diamino-3,3'-dimethyldicyclohexylmethane and19.2 g (0.098 mol) of 1,2,3,4-cyclobutane tetracarboxylic dianhydridewere reacted in 343.5 g of N-methylpyrrolidone (hereinafter referred toas NMP for short) for 10 hours at room temperature to prepare apolyimide precursor (polyamic acid) solution. The polymerizationreaction proceeded easily and uniformly, and a polyimide precursorhaving a reduced viscosity of 0.78 dl/g (as measured in NMP at atemperature of 30° C. and at a concentration of 0.5 g/dl), was obtained.

This solution was diluted with NMP to a total solid content of 4 wt %.Then, the solution was spin-coated at 3500 rpm on glass substrates andthen subjected to heat treatment at 80° C. for 5 minutes and at 250° C.for one hour to form polyimide resin films having a thickness of 1000 Å.The coating films were rubbed with a cloth, and the substrates subjectedto such rubbing treatment were assembled with a spacer of 2 μminterposed therebetween so that the respective rubbing directions are inparallel with each other, and ferroelectric smectic liquid crystal(CS-1014, manufactured by Chisso Co.) was injected into the space toobtain a surface-stabilized liquid crystal cell. The alignment conditionof the cell was observed by a polarization microscope, whereby manyzigzag defects and linear defects were found, and the alignment offerroelectric liquid crystal was uniform.

COMPARATIVE EXAMPLE 5

11.6 g (0.1 mol) of 1,6-diaminohexane and 19.2 g (0.098 mol) of1,2,3,4-cyclobutane tetracarboxylic dianhydride were reacted in 174.5 gof N-methylpyrrolidone (hereinafter referred to as NMP for short) for 10hours at room temperature, and it was tried to prepare a polyimideprecursor (polyamic acid) solution. However, since a salt was formed dueto high basicity of 1,6-diaminohexane, the polymerization reaction didnot proceed uniformly. Further, even if the amount of acid anhydridecharged was the same, a salt was formed due to high basicity of1,6-diaminohexane, and the formation of the salt was not quantitative,whereby the viscosity of polyimide precursors obtained was different ineach polymerization. As an example of polyimide precursors havingdifferent viscosity, a polyimide precursor having a reduced viscosity of0.5 dl/g (as measured in NMP at a temperature of 30° C. and at aconcentration of 0.5 g/dl), was obtained.

This solution was diluted with NMP to a total solid content of 6 wt %.Then, the solution was spin-coated at 3000 rpm on glass substrates andthen subjected to heat treatment at 80° C. for 5 minutes and at 250° C.for one hour to form polyimide resin films having a thickness of 1000 Å.

The coating films were rubbed with a cloth and assembled with a spacerof 50 μm interposed therebetween so that the respective rubbingdirections are opposingly in parallel with each other, and nematicliquid crystal (ZLI-2293, manufactured by Merck Co.) was injected intothe space to obtain a liquid crystal cell.

The alignment condition of the liquid crystal cell was observed by apolarization microscope, and confirmed to be uniform with no defect.Further, with regard to the cell, the tilt angle of liquid crystal wasmeasured by a crystal rotation method and found to be 1.9°.

Further, the liquid crystal cell was subjected to heat treatment in anoven at a temperature of 120° C. for one hour, and the alignmentcondition was observed by a polarization microscope, whereby an uniformalignment with no defect was found out. However, with regard to thecell, the tilt angle of liquid crystal was measured by a crystalrotation method and found to be 2.5°. Thus, the tilt angle became highby the heat treatment, and a low tilt angle could not be obtained afterheat treatment.

COMPARATIVE EXAMPLE 6

11.6 g (0.1 mol) of 1,6-diaminohexane and 19.2 g (0.098 mol) of1,2,3,4-cyclobutane tetracarboxylic dianhydride were reacted in 174.5 gof N-methylpyrrolidone (hereinafter referred to as NMP for short) for 10hours at room temperature, and it was tried to prepare a polyimideprecursor (polyamic acid) solution. However, since a salt was formed dueto high basicity of 1,6-diaminohexane, the polymerization reaction didnot proceed uniformly. Further, even if the amount of acid anhydridecharged was the same, a salt was formed due to high basicity of1,6-diaminohexane, and the formation of the salt was not quantitative,the viscosity of polyimide precursors obtained was different in eachpolymerization. As an example of polyimide precursors having differentviscosity, a polyimide precursor having a reduced viscosity of 0.5 dl/g(as measured in NMP at a temperature of 30° C. and at a concentration of0.5 g/dl), was obtained.

This solution was diluted with NMP to a total solid content of 6 wt %.Then, the solution was spin-coated at 3000 rpm on glass substrates andthen subjected to heat treatment at 80° C. for 5 minutes and at 250° C.for one hour to form polyimide resin films having a thickness of 1000 Å.Then, the coating films were rubbed with a cloth, and a pair ofsubstrates subjected to such rubbing treatment, were assembled with aspacer of 2 μm interposed therebetween so that the respective rubbingdirections are in parallel with each other, and ferroelectric smecticliquid crystal (CS-1014, manufactured by Chisso Co.) was injected intothe space to obtain a surface-stabilized liquid crystal cell. Thealignment condition of the cell was observed by a polarizationmicroscope, and no defects was found at any region of the liquid crystalcell, whereby an uniform alignment of ferroelectric liquid crystal wasconfirmed. However, although the alignment of ferroelectric liquidcrystal was good, a salt was formed since 1,6-diaminohexane is highlybasic. Further, since the formation of the salt was not quantitative,the viscosity of polyimide precursors obtained was different in eachpolymerization. Therefore, it was difficult to prepare a polyimideprecursor which was highly reproducible.

INDUSTRIAL APPLICABILITY

By the treating agent for liquid crystal alignment of the presentinvention, it is possible to obtain a liquid crystal alignment filmhaving a low tilt angle and being thermally stable, and to obtain aliquid crystal device having higher contrast as compared withconventional one. Further, by using the treating agent for liquidcrystal alignment of the present invention, a ferroelectric liquidcrystal display device and an antiferroelectric liquid crystal displaydevice exhibit excellent properties.

What is claimed is:
 1. An alignment treating agent for a liquid crystal cell, which is composed mainly of a polyimide, a polyimide precursor or a mixture thereof, wherein said polyimide or precursor thereof is made by a polymerization reaction of a tetracarboxylic acid derivative component with a diamine component, wherein at least one part of the diamine component is a diamine component of the following formula (1): ##STR6## wherein n is an integer of from 1 to 12, and which gives a tilt angle of at most 2° to nematic liquid crystal.
 2. The alignment treating agent for a liquid crystal cell according to claim 1, wherein the diamine of the formula (1) in the diamine component is at least 50 mol % to the total diamine component.
 3. The alignment treating agent for a liquid crystal cell according to claim 1, wherein the tetracarboxylic acid derivative component is at least one tetracarboxylic acid derivative selected from the group consisting of an aromatic tetracarboxylic acid derivative and a cyclobutane tetracarboxylic acid derivative.
 4. The alignment treating agent for a liquid crystal cell according to claim 1, wherein in the diamine compound of formula (1) n is an integer of 3 to
 12. 5. The alignment treating agent for a liquid crystal cell according to claim 1, wherein the diamine component consists essentially of the diamine component of formula (1). 